1. Field of the Invention
The present invention relates to a defect coordinates measurement device, a defect coordinates measurement method, a mask manufacturing method, and a reference mask.
2. Description of Related Art
When forming a fine pattern in an EUVL (Extreme UltraViolet Lithography) mask or the like, an alignment mark (fiducial mark) is used for the alignment (Japanese Unexamined Patent Application Publication No. 2005-50851). In the technique disclosed in Japanese Unexamined Patent Application Publication No. 2005-50851, a cross alignment mark is formed by cutting a groove on a substrate and depositing chromium oxide into the groove.
In a manufacturing process of a semiconductor device, if a mask defect is printed onto the semiconductor device, conduction or short-circuit of wires occurs, which results in a defective item. Japanese Unexamined Patent Application Publication No. 2011-9662 discloses a technique of detecting a defect by forming a grid on the backside of an element formation surface of a semiconductor substrate.
In the case of implementing defect mitigation in EUVL, the total tolerance of the alignment is 20 nm, for example. Thus, it is necessary to detect a defect highly accurately. However, when detecting a defect, various errors are present in measurement results. The errors include an offset error and rotation error when placing a sample on a stage, the orthogonality and straightness of a stage, a magnification error and the like, for example.
Further, the distortion of straightness of a stage can be corrected by a polynomial approximation. In this case, by using higher-order terms in a polynomial approximate expression, the accuracy can be enhanced. However, in actual measurements, not only a low-order offset error and rotation error but also a high frequency component such as a white noise occurs. Thus, the polynomial approximation causes an error to be raised at the end of a mask, which decreases the accuracy.
Further, in order to reduce an error in stage coordinates to be 20 nm or less, there is a problem of temperature stability or the like. To maintain the coordinate accuracy for a long time, costs increase because of an increase in device size due to a temperature stabilization mechanism and use of a low thermal expansion material. There is thus a problem that the measurement accuracy of defect coordinates decreases with a simple device configuration and a coordinate system calibration method.
The present invention has been accomplished to solve the above problems and an object of the present invention is thus to provide a defect coordinates measurement device capable of highly accurate measurement, a defect coordinates measurement method, a mask manufacturing method, and a reference mask.